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* Re: unfair servicing of DomU vbd requests
@ 2011-03-03  8:30 Keir Fraser
  2011-03-03 17:09 ` [GIT/PATCH 0/5] " Ian Campbell
  0 siblings, 1 reply; 14+ messages in thread
From: Keir Fraser @ 2011-03-03  8:30 UTC (permalink / raw)
  To: James Harper, Ian Campbell; +Cc: xen devel

On 03/03/2011 08:28, "James Harper" <james.harper@bendigoit.com.au> wrote:

>>>> It appears that Dom0 is not servicing vbd requests from DomU's fairly so
>>>> one or two end up getting stalled while the others are mostly okay. How
>>>> are vbd requests supposed to be serviced? Is there potential for one to
>>>> be overlooked for a long period of time? Is there some settings that
>>>> could be changed to avoid this happening?
>>> 
>>> Dom0 does round-robin scanning of pending event channels these days, which
>>> helps fairness a fair bit.
>> 
>> I have a feeling this isn't true of pvops kernels...
>> 
>> looks like we need to pull 324:7fe1c6d02a2b (and subsequent fixes) out
>> of 2.6.18-xen.hg into the pvops world.
>> 
> 
> I hope that's true and easy to fix. It would certainly explain why one DomU
> can starve enough to the point where it's IO doesn't get serviced for >70
> seconds.

Without the round-robin servicing, unfairness to the point of starvation is
a distinct possibility.

 -- Keir

> Thanks for looking at this.
> 
> James

^ permalink raw reply	[flat|nested] 14+ messages in thread

end of thread, other threads:[~2011-03-09  5:38 UTC | newest]

Thread overview: 14+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
     [not found] <AEC6C66638C05B468B556EA548C1A77D01C55BC6@trantor>
2011-03-04  7:12 ` [GIT/PATCH 0/5] Re: unfair servicing of DomU vbd requests MaoXiaoyun
2011-03-04  7:21   ` Ian Campbell
2011-03-04  9:59     ` MaoXiaoyun
2011-03-04 10:06       ` Ian Campbell
2011-03-07  3:37         ` MaoXiaoyun
2011-03-07  8:09           ` Ian Campbell
2011-03-07 10:20             ` MaoXiaoyun
2011-03-08  2:04 ` MaoXiaoyun
2011-03-08  2:22   ` James Harper
     [not found]   ` <AEC6C66638C05B468B556EA548C1A77D01C55D47@trantor>
2011-03-09  5:38     ` MaoXiaoyun
2011-03-03  8:30 Keir Fraser
2011-03-03 17:09 ` [GIT/PATCH 0/5] " Ian Campbell
2011-03-04  8:40   ` John Weekes
2011-03-04  9:15     ` Ian Campbell
2011-03-07 19:33       ` John Weekes

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